Electron discharge device and circuit



Feb. 29, 1944. B. SALZBERG ELECTRON DISCHARGE DEVICES AND CIRCUITS Filed May 31, 1941 4 Sheets-Sheet l INVENTOR 125 i- 60 f 32!; ATTO R N EY Feb. 29, 1944. s. SALZBERG ELECTRON DISCHARGE DEVICES AND CIRCUITS Filed May 51, 1941 4 Sheets-Sheet 2 INVENTOR flgrlmzddahaely BY 7g ATTORNEY Feb. 29, 1944. B. SALZBERG ELECTRON DISCHARGE DEVICES AND CIRCUI Filed May 31, 1941 5/15. 19% J'QQB/ 4 Sheets-Sheet 3 l 19 afid wzaecaazr lgl} INVENTOR Ber/wyZJhZzJeIy ATTO R N EY Feb. 29, 1944. SALZBERG 2,342,896.

ELECTRON DISCHARGE DEVICES AND CIRCUITS Filed May 31, 1941 4 Sheets-Sheet 4 We orfwerhbn Patented Feb. 29, 1944 ELECTRON DISCHARGE DEVICE AND CIRCUIT Bernard Salzberg, East Orange, N. .L, ass ignoi: to Radio Corporation of American, a corporation of Delaware Application May 31, 1941, Serial No. 396,021

24 Claims.

This invention relates to oscillation generators for short Waves, and particularly to generators employing vacuum tubes having multiple leads for the different electrodes.

An object of the present invention is to provide a highly eificient ultra short wave generator circuit employing a vacuum tube having a plurality of leads for each of the grid and plate electrodes.

Another object is to provide means for making most effective use of vacuum tubes in which a plurality of leads are provided for each of the electrodes which carry radio frequency currents.

A further object is to provide a highly stable oscillation generator for use in the wavelength range from approximately 40 centimeters to 2 meters, more or less.

Although the present invention is hereinafter described in connection with electron discharge devices of the triode type whose grid and anode electrodes each have a pair of terminal connections or leads extending from opposite sides of the envelope, it should be distinctly understood that the invention is not limited to the use merely of a pair of such leads for each electrode since obviously more than two leads can be used for each of the electrodes, or the leads for each electrode can be replaced by a continuous metallic surface.

In the preferred embodiment of the invention, there is employed one or more electron discharge devices of the vacuum tube type wherein the grid and anode of each device are each provided with a plurality of terminal connections and there is coupled to these terminal connections a low loss tank circuit consisting of metallic sheets of highly electrical conducting material suitably coupled together. Where a single vacuum tube is employed for the oscillation generator, this tube may be connected either at one end of the fiat sheet constituting the tank circuit, or at some intermediate point, and if the latter, preferably in the electrical center of the sheets. Where the oscillation generator is of the pushpull type, however, the vacuum tubes may be connected at opposite ends of the sheets constituting the low loss tank circuit.

A more detailed description of the invention follows, accompanied by drawings wherein:

Figs. 1a, 2a and 3a illustrate different embodiments of the invention;

Figs. 1b, 2b and 3b schematically illustrate respectively the equivalent electrical circuits for the circuits of Figs. 1a, 2a, and 3a;

Figs. 4, 5 and 6 illustrate still further embodiments of the present invention; and

Fig. 7 illustrates, by Way of example only, one way in which each sheet of the tank circuits of Figs. la, 2a, 3a and 4 can be constructed to provide adjustability.

Throughout the figures, the same or equivalent parts are represented by the same reference numerals.

Referring to Fig. la in more detail, there is shown an electron discharge device I having an anode A, a grid G, and a filament F. It should be noted that there are provided two terminals or leads for each anode and grid and a center tap to the filament. A tube of this type is marketed under the trade name RCA 1628, although it should be understood that any other suitable type of tube having a multiplicity of lead or terminal connections for the grid and anode electrode can be used. Connected to both terminals of the grid G is a thin metallic sheet L1 of highly electrical conducting material and similarly connected to both terminals of the anode A is another metallic sheet L2 of highly electrical conducting material. Sheets L1 and L2, each somewhat shOrter in length than onequarter wavelength at the operating frequency, can be made of copper, or any suitable metal plated with silver, copper or gold. In one embodiment actually tried out in practice the sheets consisted of copper suitably plated with silver. The sheets L1 and L2 are separated at one end by a mica sheet to form a capacitor C whose reactance at the operating frequency is extremely low. It will thus be obvious that the capacitor C provides a short circuit between the conductors L1 and L2 for the operating frequency. The filament leads for heating the filament are separately enclosed in a tubular conductor 2 from which they are insulated. This tubular conductor forms the inner conductor of a coaxial transmission line whose outer con ductor is 2', both conductors of which are bridged by a sliding short circuiting disc 3. The center tap for the filament F is directly connected to the free end of the inner conductor 2 while the filament legs are capacitively coupled to this same free end by means of radio frequency by-pass capacitors 4. Capacitors 4 spacing relative to the sheet L2.

larizing potentials are supplied to the anode and grid of the tube by means of connections 5 and 6. It is preferred that each of the connections 5 and 6 be supplied with an anti-parasitic network composed of a resistor in shunt with an inductor in order to prevent spurious oscillations which might otherwise take place along the supply leads. A grid leak 8 in series with the network 1 provides the polarizing bias for the grid. In order to abstract energy from the oscillator, there is shown a suitable output circuit 9 which is coupled to the tank L1, L2 by means of a loop ii) extending through a suitable slot in one of the metal sheets in the center thereof. Alternatively, the energy may be abstracted from the oscillator by means of a similar arrangement extending between the conductors of the coaxial line forming the filament tuning circuit. A grounded metallic shield H surrounds the oscillator for preventing undesired radiation or losses which would otherwise be brought about by proximity to neighboring bodies.

The filament is supplied with heating current by means of a suitable source, such as a battery or low frequency alternating current source, connected to the two insulated leads l2 which extend through the entire length of the inner conductor 2 to connect with the legs of the filament. The metallic sheets L1 and L2, together with the capacitor form, in effect, a highly efficient low loss oscillatory circuit (tank). By using both terminals of the grid G and both terminals of the anode A symmetrically relative to the sheets in the manner shown, I am able to reduce to a very considerable extent the deleterious effects of the lead impedances of the grid and anode electrodes. The coaxial line constituting the filament tuning circuit functions as a control for varying the excitation on the grid, thus obtaining optimum efiiciency andmaximum power output. This method of controlling the excitation on the grid by means of movement of the disc 3 does not, however, materially change the frequency of oscillation of the oscillator.

A better understanding of the operation of Fig. la may be had by referring to the equivalent electrical circuit shown in Fig. 1b. In Fig. 1b the net eiiect of the impedances of sheets L1 and L2 are represented schematically by the equivalent electrical circuit comprised of inductances L1 and L2 and capacitance It. This circuit forms the main oscillatory circuit for the oscillator. The net effect of the filament tuning transmission line of Fig. lb is represented by the lumped circuit 2, 2', 3 of Fig. lb.

The equivalent electrical circuit of Fig. lb will be recognized by those skilled in the art as a well known type of ultra audion or Colpits type of oscillator. By means of my novel concept of connecting the sheet metal type of tuned circuit to both terminals of the grid and both terminals of the anode, I have been able to effect a significant improvement in the operation of this generic type of oscillator circuit, as shown in Fig. 11).

Fig. 2a shows the principles of the invention applied to a push-pull circuit. To those skilled in the art, Fig. 2a represents a symmetrical pushpull extension of the single ended circuit of Fig. 1a. In this figure, there are shown two tubes I, I, generally of the type shown in Fig. 1, connected to opposite ends of a pair of sheets L1, L2 constituting the tank circuit. It should be noted that the by-pass condenser C of Fig. 1a is dispensed with in Fig. 2, and the leads and 6 supplying polarizing potentials to the grids and anodes are connected to the electrical and physical points of symmetry of the metallic sheets L1 and L2, as shown. The filament tuning circuits for tubes l of Fig. 1a are respectively separately enclosed in tubular conductors l4, l4 constituting a circuit l5 which is bridged by a shorting bar or bridge iii grounded at its center for radio frequency energy, as shown. It should be noted that the center tap for each filament is directly connected to the free end of its associated tubular conductor M while the legs of the filament extend through the lengths of the tubular conductor i l to the filament heating transformer ll. Another way of tuning the filament is to supply each of the filament circuits with separately adaptable coaxial transmission lines, as shown in Fig. 1a. Energy may be abstracted from the oscillator of Fig. 20. either from the filament tuning circuit by means of leads IE or else by means of a line Iii symmetrically connected to anode sheet L2. A suitable grounded shield 23 surrounds the push-pull oscillator of Fig. 1b.

Fig. 2b shows the equivalent electrical circuit diagram of Fig. 2a. Inspectionoi this figure will make it apparent that this oscillator is essentially a symmetrical or push-pull type of Colpits oscillator and is the image extension of Fig. 1b.

Fig. 3a is a modification of the oscillator of Fig. 1a and is similar thereto except for the manner in which the excitation of the grid is varied for obtaining optimum efiiciency and maximum power output. In Fig. 3a the excitation on the grid is varied by means of a metallic sheet L3 of substantially the same material as sheets L1 and L2 but coupled at one end to an extension of the anode sheet L2 and directly connected at its other end to the center tap on the filament. The sheet L3, it should be noted, is provided with flanges at both ends, one of which is adjacent to and spaced from the extension of sheet L2 to provide a capacitance coupling therebetween, indicated by capacitor C2. For tuning purposes, the spacing between the sheet L3 and the extension of sheet L2 can be varied in order to vary the degree of capacitive coupling. It is sometimes desirable to provide means for varying the actual length of the sheet L3. The method by which this sheet can be varied in length is described hereinafter in connection with Fig. 7.

The equivalent electrical circuit for Fig. 3a is shown in Fig. 3b. Except for the method of tuning, the operation of the circuit of Fig. 3b is the same as that described above in connection with Fig. lb.

Fig. 4 illustrates a still. further modification of the invention wherein the low loss tank circuit comprising the sheets L1 and L2 have been extended in length and the vacuum tube I- placed in the electrical and physical center of these sheets. Effectively, the entire length of the tank circuit in conjunction with the vacuum tube capacitances is electrically one-half wavelength at the operating frequency. By means of the arrangement shown in Fig. 4, I am thereby able to use longer sheets (in eiTect a longer transmission line) for a given wavelength, thus permitting the oscillator to go to shorter wavelengths or, for a given wavelength to operate with greater efficiency and. power output. The reason for this further improvement resides in the fact that still more efiective use is obtained, by virtue of a double sheet construction of the multiple grid and anode leads. Except for the foregoing difierences, the operation of the oscillator of Fig. 4 is substantially identical with that described in Figs. 1a and 1b, and it should be noted that the ends of the sheets L1, L2 constituting the low loss tank circuit are short circuited for the operating radio frequency in the same manner as the one end of the sheets of Fig. 1a. The vacuum tube and filament tuning system have not been shown in order to simplify the drawing.

Still further circuit improvements over Fig. 4 are effected by using the tank circuit arrangements shown in Figs. 5 and 6, wherein the straight flat sheets have been replaced by the circular disc arrangements L2 and L1" in Fig. 5, and by the deformed toroidal arrangement L4, L5 in Fig. 6. The improvements in Figs. 5 and 6 are obtained by virtue of the fact that additional highly electrical conducting material has been provided for the tank circuit, thus providing more highly efiicient low loss tank circuits. The vacuum tubes have not been shown connected to the tank circuits of Figs. 5 and 6 in order to simplify the drawing. Fig. 6 is a sectional view and hence only shows one of each of the two grid and anode terminals. Alternative types of output loops have been shown in Fig. 6.

Fig. 7 shows one way by which the length of each of the sheets of Figs. 1a, 2a, 3a. and 4 can be adjusted. The sheet of Fig. '7, in effect comprises telescoping arrangements of elements 20 and 2|, one of which (namely 2|) has overlapping sides to enable the other sheet (namely 20) to slide therewithin, and is also provided with contact fingers 23 for insuring good electrical contact between the telescoping elements of the sheet. Since the sheet tank circuits operate by virtue of their distributed inductance and capacitance, thus causing a distribution of voltage and current along their length, it is highly desirable, for reasons of highest eificiency and lowest losses, to insure that the contact fingers 23 be placed at a point on the sheet transmission line where current density is a minimum.

The dimensions of the tank circuits of all the figures may be obtained by proper engineering calculations, or, if necessary, by cut-and-trial.

Although several different ways have been shown for abstracting energy from the oscillators, it should be understood that in all and any of the figures throughout the drawing the energy may be abstracted either capacitively, inductively or conductively, or any combination thereof.

It should be understood that the invention is not limited to the precise arrangements of parts shown, since various modifications may be made without departing from the spirit and scope thereof. For example, the sheets of the various figures, whether flat or deformed, may or may not be of the same length, since obviously it may be desirable to locate the radio frequency by-passing capacitor between the sheets of the tank at a point unsymmetrically arranged with respect to the physical plane of symmetry of the sheets, but preferably as closely as possible to the position of the radio frequency voltage node.

What is claimed is:

1. A tank circuit for an electron discharge device having grid and anode electrodes contained within an evacuated envelope, each electrode of which is provided with a pair of terminal leads extending from opposite sides of the envelope, comprising a pair of sheets of highly electrical conducting material extending at right angles to the longitudinal axis of said device, one sheet of which is directly connected symmetrically to the grid terminals in parallel relation, and the other sheet of which is directly connected symmetrically to the anode terminals in parallel relation.

2. A tank circuit in accordance with claim 1, characterized in this that said sheets are flat.

3. A tank circuit in accordance with claim 1, characterized in this that said sheets are deformed to increase the surface area thereof.

4. A tank circuit for an electron discharge device having anode and grid electrodes, each of which is provided with a plurality of terminal leads, comprising substantially similar coextensively arranged sheets of highly electrical conducting material, one sheet of which is directly connected symmetrically to the grid terminals and extend on opposite sides of the tube envelope and the other sheet of which is directly connected symmetrically to the anode terminals and extend on opposite sides of the tube envelope, whereby said tube is arranged in the electrical and physical center of said tank, said sheets having individual terminal fittings for the different terminal leads of said electrodes.

5. A tank circuit as defined in claim 4, charac terized in this that said sheets are fiat and are connected together at their ends through paths of low impedance to currents of the operating frequency.

6. A tank circuit as defined in claim 4, characterized in this that said sheets comprise parallel circular discs.

7. A tank circuit in accordance with claim 4, characterized in this that the over-all assembly of said sheets constitutes a toroid.

8. A tank circuit in accordance with claim 4, characterized in this that the said sheets are deformed and connected together at their ends by paths of low impedance to currents of the operating frequency to constitute a toroid, said paths of low impedance comprising spaced flanges suitably spaced to provide a capacitive effect.

9. A tank circuit for an electron discharge device having grid and anode electrodes within an evacuated envelope, each electrode of which is provided with a pair of terminal leads extending from substantially opposite sides of the envelope of the device, comprising a pair of rectilinear sheets of highly electrical conducting material, one sheet of which is directly connected at one end symmetrically to the grid terminals in parallel relation, and the other sheet of which is directly connected at one end symmetrically to the anode terminals in parallel relation, said ends of said sheets having cut out portions for accommodating the envelope of said device and for minimizing the lengths of the connections between said electrodes and said sheets.

10. A tank circuit for an electron discharge device having grid and anode electrodes, each electrode of which is provided with a plurality of terminal leads extending from substantially opposite sides of the envelope, comprising a pair of equal length rectilinear sheets of highly electrical conducting material, one sheet of which is directly connected symmetrically to the grid terminals in parallel relation, and the other sheet of which is directly connected symmetrically to the anode terminals in parallel relation.

11. A tank circuit for a pair of electron discharge devices, each device of which has aneode, cathode and grid electrodes within an evacuated envelope, said anode and grid electrodes being each provided with a plurality of termi nal leads extending from substantially opposite devices, said sheets having cut out portions for accommodating the envelopes of said devices, thereby minimizing tions between the terminal leads of said electrodes and said sheets.

12. A tank circuit as defined in claim 11, characterized in this that said sheets are each electrically one-half wavelength long at the operating frequency.

13. A tank circuit for an electron discharge device having grid and anode electrodes within an evacuated envelope, each electrode of which is provided with a pair of terminal leads extending from substantially opposite sides of the envelope, comprising a pair of rectilinear sheets of highly electrical conducting material, one sheet of which is directly connected symmetrically to the grid terminals in parallel relation, and the other sheet of which is directly connected symmetrically to the anode terminals in parallel relation, said sheets being of unequal physical length and having cut out portions for accommodating the envelope of said device, thereby minimizing the lengths of the connections between the terminal leads of said electrodes and said sheets.

14. In combination, an electron discharge device oscillator having grid, anode and cathode electrodes, said grid and anode electrodes being each provided with a plurality of terminal leads, a tank circuit for said oscillator comprising a pair of substantially coextensive sheets of highly electrical conducting material, one sheet of which is directly connected symmetrically to the grid terminals in parallel relation, and the other sheet of which is directly connected symmetrically to the anode terminals in parallel relation, connections to said sheets for supplying suitable bias to said grid and anode electrodes, and tuning means connected to said cathode forvarying the excitation on said grid.

15. Apparatus in accordance with claim 14, characterized in this that said tuning means connected to said cathode includes a metallic tubular conductor surrounding the cathode leads, and an adjustable connection from said tubular conductor to ground.

16. In combination, an electron discharge device oscillator having grid, anode and cathode electrodes, said grid and anode electrodes being each provided with a plurality of terminal leads, a tank circuit for said oscillator comprising a pair of coextensive sheetsof highly electrical conducting material, one sheet of which is directly connected symmetrically to the grid terminals in parallel relation, and the other sheet of which is directly connected symmetrically to the anode terminals in. parallelrelation, connecthe lengths of the connections tq saidsheets for supplying suita e b said gridandranode electrodes,tuningmeans connected to-said-cathode for varying the excitation on said grid, and a grounded shield surroundingsaid oscillator, said tank circuit and said cathode tuning means.

17. In combination, a pair of electron discharge devices, eachdevice of which has anode, cathode and grid electrodes, said anode and grid electrodes being-eachprovided with a plurality of terminal leads, a tank circuit comprising a pair of spaced, coextensive sheets of highly electrically conducting material, one sheet of which is directly connected at opposite ends to the grid terminal leads of said devices in parallel relation,

andtheother sheet of which is directly con-,

nected at opposite ends to the anode terminal leads of said devices in parallel relation, connections to the physical and electrical points of symmetry of said sheets for supplying polarizing potentials to said anode and grid electrodes, and

means for tuning the cathode circuits of said devices, and a grounded shield surrounding said devices, said tank circuit and said cathode tuning means.

18. In combination, a pair of electron discharge devices each having an anode, a cathode and a grid within an evacuated envelope, said grid and anode electrodes being each provided with a pair of terminals extending from opposite sides of the surrounding envelope, a tank circuit comprising a pair of spaced coextensive sheets of highly electrical conducting material, one sheet of which is directly connected at one end to the grid terminals of one device and at the other end directly connected to the grid terminals of the other device, and the other sheet of which is directly connected at one end to the anode terminals of one device and at the other end directly connected to the anode terminals of the other device, connections to th physical and electrical points of symmetry of said sheets for supplying suitable bias potentials to said anode and grid electrodes, heater leads for each cathode, a tubular shield for the heater leads of each cathode, and means ontacting the tubular shields and movable over the lengths thereof for connecting said shields to a point of fixed radio frequency potential.

19. In combination, a pair of vacuum tubes eachhaving an anode, a cathode anda grid, the anode and grid electrodes each having a pair of terminals extending from difierent portions of the envelope, a tank circuit comprising two similar coextensive metallized sheets, located one above the other, one sheet being directly connected at one edge to the grid terminals of i one tube and directly connected at its opposite edge to the grid terminals of the other tube, and the other sheet being directly connected at one edge tothe anode terminals ,of one tube and directly connected at its opposite edge to the anode terminals of th other tube, said sheets having clips for'accomrnodating said terminals, and means for tuning said cathodes.

20. In combination, a vacuum tube having grid, anode and cathode electrodes, said gridand anode electrodes each having a pair of terminals extending from difierent portions of the tube envelope, a tank circuit having a pair of metallic substantially coextensive sheets one sheet of which is directly connected to the grid terminals and the other sheet, of which. is

directly-connec d o th .'anode,;terminals, v said:

sheets having spring clips for accommodating said terminals, and means for tuning said cathode.

21. In combination, a vacuum tube having grid. anode and cathode electrodes, said grid an anode electrodes each having a pair of terminals extending from diiferent portions of the tube envelope, a tank circuit having a pair of metallic coextensive sheets one sheet of which is directly connected to the grid terminals and the other sheet of which is directly connected to the anode terminals, said sheets being disposed at right angles to the longitudinal axis of said vacuum tube and having spring clips for accommodatin said terminals, a capacitive path of low impedance to energy of the operating frequency between said sheets at a location removed from said spring clips, and means for tuning said cathode.

22. A tank circuit for an electron discharge tube having grid and anode electrodes, each electrode of which has at least two terminals extending outward from different portions of the tube envelope, comprising a pair of metallic surfaces cooperating to form an oscillatory circuit, said surfaces being insulated from each other from a direct current standpoint, one of said surfaces having a plurality of terminal sockets for the grid terminals of said tube, while the other surface has a plurality of terminal sockets for the anode terminals of the tube.

23. A tank circuit for an electron discharge tube having grid and anode electrodes, each electrode of which has at l ast two terminals extending outward from different portions of the tube envelope, comprising a pair of metallic coextensive surfaces cooperating to form an oscillatory circuit, said surfaces being insulated from each other from a direct current standpoint, one of said surfaces having a plurality of terminal sockets for the grid terminals of said tube, while the other surface has a plurality of terminal sockets for the anode terminals of the tube.

24. A tank circuit for an electron discharge tube havin grid and anode electrodes, each electrode of which has at least two terminals ex tending outward from different portions of the tube envelope, comprising a pair of. metallic surfaces cooperating to'form an oscillatory circuit, said surfaces being insulated from each other from a direct current standpoint, one of said surfaces having a plurality of terminal sockets for the grid terminals of said tube, While the other surface has a plurality of terminal sockets for the anode terminals of the tube, said surfaces having cut out portions for enabling the tube envelope to be at least partially surrounded by said surfaces.

BERNARD SALZBERG. 

